O'Fallon, Illinois

O'Fallon, Illinois
The Illinois Central Railroad Downtown Caboose
Nickname: 
"O-Town"
Location of O'Fallon in St. Clair County, Illinois.
Coordinates: 38°35′51″N 89°54′37″W / 38.59750°N 89.91028°W / 38.59750; -89.91028!-- Area/postal codes and others -->
CountryUnited States
StateIllinois
CountySt. Clair
TownshipO'Fallon
Government
 • TypeHome rule
Area
 • Total
15.70 sq mi (40.67 km2)
 • Land15.59 sq mi (40.39 km2)
 • Water0.11 sq mi (0.29 km2)
Elevation
538 ft (164 m)
Population
 (2020)
 • Total
32,289
 • Density2,070.6/sq mi (799.48/km2)
Time zoneUTC−6 (CST)
 • Summer (DST)UTC−5 (CDT)
ZIP code
62269
Area code618
FIPS code17-55249
GNIS feature ID2395302
Websiteofallon.org

O'Fallon is a city in St. Clair County, Illinois, United States. The 2020 census listed the population at 32,289. The city is the second largest city in the Metro East region and Southern Illinois. It sits 5 miles (8.0 km) from Scott Air Force Base and 18 miles (29 km) from Downtown St. Louis.

Like its namesake in St. Charles County, Missouri, O'Fallon is part of the St. Louis metro area. This makes O'Fallon (along with the two Troys in Illinois and Missouri) one of the few pairs of like-named municipalities to be part of the same metro region.